Mechanism of flame stabilization in turbulent, lifted-jet flames
- Sandia National Labs., Livermore, CA (United States). Combustion Research Facility
Particle image velocimetry was used to study the velocity field in the stabilization region of lifted, turbulent CH{sub 4}-jet flames over a range of Reynolds numbers from 7,000 to 19,500. Measured velocities at the flame base are considerably below the turbulent flame speeds derived from previous studies and show a dependence on the Reynolds number. The average velocity at the stabilization point is nearly a factor of five below the premixed laminar burning velocity at the lowest Reynolds number and asymptotes to a value about 20% higher as the Reynolds number is increased. Planar images of OH show that the flame zone structure near the stabilization point is also highly dependent on the Reynolds number. Comparison of the present OH images with previous CH{sub 4} Raman imaging results shows that the flame thickness is determined by the width of the flammable region. At a low Reynolds number, the flame is stabilized near the jet exit where the flammable layer is thin, resulting in a thin flame zone. At an increased Reynolds number, the stabilization point is located farther downstream where the flammable region is wider, resulting in a correspondingly wider flame zone. It is proposed that the lower velocities observed at the flame base are related to thinning of the flame zone at low Reynolds, which results in greater curvature of the flame base. The increased flame curvature effectively defocuses the transport of heat and flame radicals to reactants upstream of the propagating flame front, resulting in reduced burning velocities. The implications of these results for mechanisms controlling turbulent flame stabilization, with an emphasis on the applicability of triple flame concepts to turbulent flows, are discussed.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 619590
- Journal Information:
- Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 4 Vol. 112; ISSN CBFMAO; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
Similar Records
Temporal evolution of turbulence/chemistry interactions in lifted, turbulent-jet flames
Investigation of local flame structures and statistics in partially premixed turbulent jet flames using simultaneous single-shot CH and OH planar laser-induced fluorescence imaging